Instabilities of the wrist.

Carpal instability is the result of ligamentous injury to the wrist. Although any ligament may be injured, certain recurring patterns are frequently seen. Common to the treatment of all instability patterns is the need to transfer load from the capitate to the radius: reliably, without stressing normal joints, and while preserving functional motion. Limited wrist arthrodesis fulfills these needs. The radius and carpal bones are shaped so that in their "normal" position, they are preloaded. Were it not for complex ligamentous systems, the bones would immediately assume unloaded "neutral anatomic" positions. Because the shape of the wrist bones tends to displace them with significant forces, current ligamentous reconstructions are inadequate. Common radial side instabilities invariably lead to degenerative arthritis.